This application is Section III of the renal program project, T. E. Andreoli, prinicipal investigator. By ysing separated apical and basal-lateral membrane vesicles of canine inner medulla studies will be carried out on: Na ion, K ion, Cl ion transport pathways of the two membranes; 2. H plus/OH minus transport pathways in the two membranes, hence developing biochemical models for ion flow across this epithelium. Then by: 1. studies of ADH interaction with transport systems in basal-lateral membranes, 2. studies of soluble and bound protein kinases, 3. studies of water permeability of both membranes and 4. studies of membrane fluidity, it will be possible to develop biochemical models of ADH action on the collecting duct.